1. Field of the Invention
The present invention relates to pneumatic springs used for devices where large displacements are necessary, and which can be linearized.
2. Prior Art
In the prior art, pneumatic linear springs have been used, but obtaining linearity across a wide range of travel has been generally difficult, if not impossible.
Prior art devices which superficially resemble the present invention, but which fail to disclose the concept, include U.S. Pat. No. 3,368,499 which shows a collapsible hitch for semitrailers that are mounted on rail cars. A pair of hydraulic cylinders are mounted in this device in opposed relationship (connected rod to rod) in a toggle, and the cylinders collapse toward a horizontal position when not in use. However, use as a spring is not shown in this patent.
Additionally, U.S. Pat. No. 2,327,021 shows a cable tension regulator which has a pair of coil springs arranged at oblique angles to a center connecting member, which in turn is actuated by a hydraulic cylinder. This patent indicates that the load on the central piston remains substantially the same at all times because the springs will change in position as they compress.
Various devices also use shock absorbers in earthquake restraints. U.S. Pat. No. 3,794,277 is such a device, showing angular positioning of shock absorber devices, and U.S. Pat. No. 1,680,890 in FIG. 6 illustrates mechanical links that operate on a fluid pressure cylinder.
Other examples of the prior art include the following
U.S. Pat. Nos. 3,171,643, 3,854,706, 3,870,130, 3,876,192, 2,621,036, 3,044,292, 3,022,587.